WATCH: The "Atlantis" space shuttle completes its final return to Earth.

The space shuttle "Atlantis" has landed back on Earth, bringing an end to the era of the space shuttle after more than three decades.

Hundreds of people gathered near the runway at the Kennedy Space Center in Florida as the "Atlantis" and four astronauts aboard landed just before sunrise on July 21. Its final mission was to resupply the International Space Station.

"Atlantis" commander Chris Ferguson told NASA ground controllers in Houston by radio after the landing that the space-shuttle program has "changed the way we view the world, and it has changed the way we view our universe."

"Mission complete, Houston," Ferguson said upon returning to Earth. "After serving the world for over 30 years, the space shuttle has earned its place in history, and it has come to a final stop,"

With the retirement of NASA's shuttle fleet, the U.S. space program will depend on Russian spacecraft to deliver astronauts to the International Space Station until a suitable replacement is developed.

NASA has said it intends to invite private firms to provide space transport services, but experts say these are unlikely to be ready to fly for at least three or four years.